Data storage systems may maintain more than one copy of data to protect against losing the data in the event of a failure of any of the data storage components. A secondary copy of data is maintained at a remote site in the event of a failure at the primary site. Secondary copies of the current data contained in the primary site are typically made as the application system is writing new data to a primary site. In some data storage systems the primary site may include a backup appliance to store the data in one or more storage devices located at the primary site and to organize and transfer the data to the secondary site. The secondary site receives inbound data from the backup appliance and transfers the data to a storage controller, storage device(s), or other computers for backup storage of the data. This type of system could be used for a disaster recovery solution where a primary storage controller sends data to a backup appliance that, in turn, offloads the transfers to a secondary storage controller at a remote site. In such backup systems, data is typically maintained in volume pairs. A volume pair is comprised of a volume in a primary storage device and a corresponding volume in a secondary storage device that includes an identical copy of the data maintained in the primary volume. Typically, the primary volume of the pair will be maintained in a primary direct access storage device (DASD) and the secondary volume of the pair is maintained in a secondary DASD shadowing the data on the primary DASD. A primary storage controller may be provided to control access to the primary storage and a secondary storage controller may be provided to control access to the secondary storage. The backup appliance also maintains consistent transaction sets between the two sites, wherein application of all the transactions to the secondary site creates a point-in-time consistency between the primary and secondary sites. The backup appliance will receive and maintain consistent transaction sets before offloading the consistent transaction sets to the secondary device. Some data storage systems avoid consistency problem by applying all data updates to the secondary site in the same order they were received from the primary. This may result in sending multiple updates to the secondary site when only one update may be necessary. Alternatively, a point in time version of the consistent transaction data may be collected by the backup appliance and then transferred to the secondary site to provide a complete consistent transaction set at the secondary site. Organizing and transferring the point in time version of the consistent transaction data sets to the secondary site in an efficient manner is needed.